Furnace



Aug. 11, 1931. J. F. scHRuMN FURNAC E Filed May 8, 1930 Aug. 11,1931. J, F SCHRUMN y 1,818,759

FURNACE Filed May 8, 195o :s sheetvsheet 2 fz We?? for' Aug. 1l, 1931. 1 F SCHRUMN 1,818,759

` FURNAGE Filed May s, 1930 l 5 sheets-sheet s ffy@ f/ dzfdrzy Patented Aug. 11, 1931 urul'raol STATES lgA'rENT OFFICE JEWETT E. SCHRUMN, or ATTLEBOEO, MASSACHUSETTS, AssIGNOR To TEOCESS ENGI- NEEEING AND EQUIPMENT CORPORATION, or ATTLEBORO, MASSACHUSETTS, A

CORPORAI'lON OF RHODE ISLAND EURNACE Application led May 8, 1930. Serial No. 450,847.

This invention relates to improvements in furnaces. More especially it has to do with furnaces employing a special atmosphere and in particular to novel devices and means for making such furnaces economical in Operation and safe from the dangers which may attend lthe use of such an atmosphere.

Heat'treatment of materials has been practiced for many years, although it is only in comparatively recent times that such. treatment has been carried out in special atmos- Y pheres. The desirability of uslngla particular gas, or a mixture 'of gases, or a vapor instead of air is'now well recognized because if theV material can be kept from` Contact with air while it is being heated and subsequently cooled, no oxidation will occur and t no formation of scale or discoloration will f take place. But the use of some Special atmospheres in furnaces of the types heretofore available is attended with considerable danger of explosion and ,with almost prohibitive loss of the atmosphere either by absolute escapeor by infiltration of air with consequent adulteration. Hydrogen gas, forexample, can be desirably employed as a Special atmosphere in the heat treatment of various materials.` Like other special atmosphere gases it is Somewhat expensive and because of the loss which hasfollowed its employment heretofore, has only been used where expense of operation is not a primary consideration. Hydrogen particularly may become an exceedingly dangerous agent if air is permitted to mix withY it in quantity suicient to cause an explosion.

This is particularly so if the mixture is permitted to Occur to any considerable extent 4 1n the chambers of a furnace, because these.k 4o chambers are usuallyat such a high 'degree of temperature as to cause spontaneous combustion of the mixture with obviously dam'- .aging results. It is to the avoidance of such dangers, coupled with the saving of the Special atmosphere and maintaining it free from undesirable additions that the present invention is directed. v

It Iis among the objects of the present invention to provide iny a furnace employing a special atmosphere certain novel featuresof construction and arrangement of parts which ,make for the safe and economical operation of the furnace, and the maintenance of an undiluted Special atmosphere. It is also an object to provide for the more eflicient treatment of work of recessed shape, especially as regards the scavenging ofthe air from the recesses. Other objects and features of the invention will be apparent las the description develops. p

A furnace embodying the features and advantages of this invention is disclosed in the accompanying drawings as illustrative of how the principles of the invention may be applied. This furnace is of lthe multiple chamber type with the chambers in horizontal. alignment. At opposite ends of the furnace are the entrance and exit doors respectively..

The front door is arranged to move vertically across the entrance opening of the furnace, and suitable cams are provided to insure its being tightly seated when closed. If the door Opens upward its lower edge is provided with a conduit having Outlets arranged so as to project a sheet or curtain of gas downward across the `entrance Opening. If the door opens downward, a similarconduit 1s located close by the upper edge of the entrancev opening for the same purpose.

This gaseous curtain serves two major pur- .poses in that it forms a barrier between the gas in the furnace and the outside airand in that it acts with scavenging effect upon` any materia-l being introduced to the furnace.

The exit or rear door of the furnace .preferably moves downward in opening. Novel .means are provided for tightly closing` this doorand for insuring its initial opening to occur primarily' along itsv top`.edge. This latter provision allows the gas of the rear chamber to flow out from the topthereof first. Just above-,this door is a pilot flame which instantly ignites the escaping gas (assuming of course that` this "gas is burnable when mixed with air) and thereby starts the combustion which continues as the is fully opened for the removal of the treated material. By thus providing for the Yignition of the gas and air mixture promptly as door they come into contact, the burningproceeds more or less rapidly as the air moves into the chamber but without an such explosion of the mixture as has heretofore attended the opening of the door in such furnaces.

Between the chambers is an intermediate door adapted when closed to substantially separate the chambers, although as will later more particularly appear it is preferable to permit of some passage of the gas from one chamber to the other Aeven when this intermediate door is shut. It is a feature of the invention that the casing of the furnace surrounding'this door is tight againstI leakage so that whether this door is open or closed no gas from the furnace can escape nor can any foreign gas, such as air, enter the furnace.

It is-intended that the patent shall cover by suitable expression' in the appended claims whatever features of patentable novelty. exist inthe invention disclosed.

In the accompanying drawings: V

Figure 1 .is a side elevation in medial section through a furnace constructed in accord-` ance with the principles of this invention;

Figure 2 is a plan of the rear or exit end of the furnace, with a portion of the casing cut away to disclose a detail. of construction;

Figure 3 is a front elevation of the furnace of Figure 1; i

Figure 4 is an elevation as on line 4.-4 of Figure 1, with a portion of the casing cut W9-YS Figure 5 is a rear elevation with` parts out away for clearness;

Figure 6 is a plan in section as on the line 6--6 of Figure 4;

Figure 7 is a perspective of the front door of the furnace shown in Figures 1 and 3 Figure 8 is a sectional view on line 8-8 of Flgure 5 showing a detail;

Figure 9 is a section on line 9-'9 of Figure 1 viewed as from the bottom looking upward;

Figure 10 is a side view of a furnace like that of Figure 1, but with parts in section to show an entrance door opening downward;

Figure 11 is a front view of the furnace of Figure 10; and i Figure 12 is a perspective of the entrance i door of Figures 1() and 11.

Referring more particularly to the drawings, the furnaceis preferably of that type having two chambers 1 and 2` in alignment so that material to be treated can be intro' duced at one end of the furnace, pass from one chamber to the other, and ultimately be removed at the other end of the furnace. The first chamber 1 has surrounding walls of heat insulatin material 3 and is provided with suitable eating means such as the electric units 4. This chamber will be hereinafter referred to as the heated chamber. The other chamber 2 is surrounded by a water jacket 5,

asienta At the entrance end of the heated chamber is a door 6 having a casing 6 with a lining of insulating material 3. This door moves vertically between the side members 8 and has cam strips 10 at its edges to engage adj ustable set screws 12 provided on the plates 14 attached to the members 8. As the door moves downward, its 'cam strips ride on these screws 12 and by their coaction force the door tightly against the' furnace wall. A; sector 16 and counterweight 18 with suitable connections with the treadle 2O enable the door to bel operated easily by the foot of the attendant, a latch 22 being provided to engage treadle 20 and hold the door open when desired.

Along the bottom of this front door is a perforated conduit 24 having its perforations 24a (see Figurev9) opening generally downward so that when a suitable gas is discharged therefrom a curtain or sheet of gas will be projected v'downward across the door opening. Preferably the gas supplied to this conduit 24 is an inert gas which will not mix or combine chemically with the gas in the chamber. If the work or-material to be introduced to the furnace is flat, or does not stand very high, thedoor need be raised but va short distance and in such a case the gas The gas flow for this curtain can be many ually controlled or may be automatically controlled in accordance with the door movement by providing an adjustable rack 25 on the frame lin position to be engaged by a gear 26 mounted on the stem of. a gas supply valve. As the door moves upward carrying with itthe conduit 24 and supply pipe 27 the gear 26 is turned to open the valve, and as the door descends the gear is rotated in the closingdirection.

The presence of this gas curtain prevents the escape of the special atmosphere gas from the heated chamber and the entra-nce of'outside air thereinto. When'this chamber contains a gas which forms a combustible mixture with air, it is desirable to use a burnable gas in conduit 24 and ignite it, upon the turning of gear 26, by a steadily burning pilot 28. This burning curtain takes care of any-mixture of the special atmosphere gas and air that may occur and thereby prevents the infiltrationf of theair to the chamber. As a.v result no explosive mixture can form in the chamber and no dilution of its special atmosphere can occur.

At the rear end f the heated chamber, and at thefront end of the cooled chamber, is an intermediate door 30 composed largely of heat insulating material 3 This doorl 'also moves upward to open being guided by '104 the angle plates 32.. The casing 34 surroundling this door forms a tight connection between the casing 36 of the heated chamber l and the casing 38 of the cooled chamber 2. The door I30 is preferably attached to a rod 40 which extends through a suitable packing box 42 at the top of the intermediate casing and has cable connection with the sector 44. A counterweight 46 and cable connection 48 to `treadle 5() also enables thissintermediate door to be operated from the front of the furnace. Whether thisl intermediate door is open or closed, no air can get into the chambers and no gas escape therefrom through the door casing 34. While .thus tight against .25 the transfer of any air to or gas from the chambers, the casing is not entirely tight with respect to the door when closed, thus enabling a slight leakage of gas from one chamber to the other to-take place, this being 50 desirable because as here arranged the special atmosphere is supplied to the cooled chamber through a conduit 52, which extends across the chamber, just rearward of the intermediate door, in a suitable recess or groove in thefloor. By not making the intermediate door too tight when closed, the supply of special atmosphere gas is always available for the heated chamber. I At the rear of the furnace the exit door 54 is mounted so as vto .move vertically downward when opening. This door is a plate provided with a yoke arm 56 pivotably connected to one endof a lever link 58. This link is also rpivotably connected near its lower end to a crank 60 attached to a shaft `62'. 4Fast to the latter are two grooved pulleys 64 and 66, one of which has a cable secured thereto which carries the weight 68 and the other of which has av cable connection i with a foot treadle 70. As the latter is depressed, the crank 60 is turned counter-clockwise as seen in Figure 1 and pulls the lever link58 generally downward, thus causing the Cdoor to slide vertically downward within its guides 72. It may be retained in its lower or open osition by the latch 74 provided for treadle 0.

When it is desired to close'the door, the 'downward pressure on the treadle `is re leased. The weight 68 thencauses the crank 60 to turn clockwise and force the link and door upward. As the latter reaches its closing' position the lower end of the link engages a pin 76 secured to the crank 60 below its plvotal connection with the link.

This engagement'in' eli-'ect makes the crank and link an integral member transmitting to the door the turning effect of the weight 68. Because of the relation of the moment arms, this transmitted force seats the door tightly against the gasket 78 surrounding the exit opening 2a, and 4 holds it tight thereagainst.

As will more particularly-hereinafter appear, it is desirable to have the rear door open initially along its top edge, and to inil sure its doing so, a spring actuated pin 80 is provided on the door near its bottom edge in position to be engaged by the lever link 58, as the door is being closed and forced toward the door against the resistance of its spring 82. As the crank begins its counter-v clockwise movement and relieves the closing pressure exerted on the door by the link, thedoor continues momentarily to remain tight- '85 ly closed along its bottom edge due to the force exerted by this spring 82 on pin 80 which is still engaged by the link 58. Moreover, the effect of this spring pressure `on the door is to cause it to turn slightly about its bottom edge as a fulcrum, thus insuring that its top edge moves away from the gasket 78 and .opens-initially along this top edge.

Tn preparing the furnace for operation, the front door is initially closed and the other doors left open. If hydrogen is to be used as the speciall atmosphere, a torch (not shown) is introduced through'the rear door so as to overlie the gas inlet pipe 52 which extends across afchannel inthe bottom of the cooled chamber nearby the intermediate door. As the hydrogen leaves the perforations of this inlet pipe and mixes with the air in the chambers the mixture is ignited by the flame of the torchand continues to burn until all the air in the chambers is used r up. As soon as this burning starts, the torch is removed and the rear door moved upward and tightly/closed. Very promptly the burningI in the chambers comes to anv end dueto lack of air, and-the chambers are then com pletely filled with the special atmosphere gas. The intermediate door is then closed.`

The heated chamber may be prematurely heated or heated after being filled with the special atmosphere gas. When its desired temperature is attained the door 6 is opened and a suitable gas discharge from conduit 24 so that it will escape downward from the perforations thereof.

The front door is thus raised, the escaping gas from the conduit 24 forming an eiective barrier or curtain across the dooi opening, and the work is then passed along the tracks 84 through this gas. curtain into the heated chamber, being thoroughly bathed by the gas curtain and scavenged of any air that may be present in its recesses or hollows. The front door 'is then closed tightly and the work submitted to the desired heat treatment. Up# 130 rod is removed and the intermediate door again closed. Another charge of material can now be placed 1n the heated chamber as heretofore described.

The work in the cooled chamber is cooled p down at any desired rate, the speed of cooling being controlled by the flow of cooling water through the jacket 5 surrounding this chamber. If any condensation occurs in this chamber it runs along the' fioor to the end groove-88 and passes thence through drain pipe 90 to the waste pail 92. The end ofthis pipe i-s normally covered by the liquid in the pail and thus is sealed against escape of the chamber gas. l/Vhen the cooling of the work is finished, the attendant begins to press downward on treadle 70. As heretofore explained, this results in an initial tipping of the door about its bottom edge, the top ledge swinging outward slightly and permitting the chamber gas to escape through the crack between the top edge and the 'gasket 78. lf this gas is combustible, as would be hydrogen when mixed with air, it is ignited by a pilot flame 94 just over the top of the door crack, and when this occurs the rear door can then be safely opened wide. 'This is so because the flame follows along into the cooled chamber` of. By thus igniting the mixture as it first forms and allowing the iiame tok travel into the cooled chamber as the entering air con tinues to make contact with the special atmosphere gas, all danger of explosion is elimy inated andthe safe opening of the cooled ber and the initial ignition of the escaping gas from the cooled chamber successfully prevents any explosions. Moreover, the mean-s provided for keeping the end doors tightly closed, together. with the gas-tight casing about the intermediate door avoids any unnecessary loss of the special gas and any adulteration thereof. rlhis enables the furnace to be operated with maximum economy.

l-nfigures 10-12 is illustrated an entrance door 6a which moves downward in opening.

lt is mounted on rods 98 adapted to slide in the guides 100 and 102. A treadle 20a is attached to thebar 104 joining the lower ends of these rods and aweight 106 is arranged to act as a counterbalance. This door is provided with cam strips 10a which act in'conjunction is also automatically controlled by the door movement. The gas valve 26a is provided with a lever 108 whose forked end is adapted to engage a pin 110 on the door. As the latter moves downward the lever is turned to open valve 26a. 1When the lever reaches the dotted position seen in Figure l1, the pin 110 can leave the slot of the forked end and continue downward with the door. When the latter rises the pin again enters the slot of the lever and causes the latter to swing so as to close the valve 26a. lf a combustible gas is used for the curtain, a pilot flame 112 is kept burning near the top edge of the door. When the latter starts lto open the combustible gas is ignited and thereafter acts as a barrier and with scavenging effect'while the door is open.

l claim:

l 1. Ak furnace having, in combination, a heated chamber and a cooled chamber in alignment, with an entrance door at one end of the heated chamber and an exit door at one end of the cooled chamber and an inter-l mediate door at the adjacenty ends of both chambers; the said entrance door being mounted to open vertically upward and being provided at its lower edge with a gas conduit having openings therein arranged to direct a gaseous curtain downward across the door opening as the door is raised.

2. A special atmosphere furnace having, in combination, a heated chamber and a cooled chamber arranged in alignment; a conduit havingopenings within said cooled chamber for admission of the special atmosphere gas; an exit door at the end of the cooled chamber arranged to open downward; and means providing aflame at the top edge of said exitl door whereby upon the door being opened,

the initial mixture of the special atmosphere gas and air isignited, and can thereafter burn without explosion as the said door is further opened. f

3. A special atmosphere furnace having, in

combination, two chambers in alignment;

means associated with one of said chambers to heat it and means associated with the other of said chambers to cool it; a conduit having openings within one of said chambers for admission of the special atmosphere gas; a

door at the entrance of the heated chamberl arranged to open'vertically upward and havmeans at its bottom'edge to provide a gaseous curtain across the door opening and thereby prevent escape of the special atmosphere gas therethrough; a gas tight casing connecting the adjacent ends of said chambers; an intermediate door mounted in said casing and adapted to be moved therein and having con.-

' nection with means outside said casing whereby its movements can be eiiected; a door at theexit end of said'furnace arranged to move vertically downward in opening; and means at the upper edge of the last mentioned door for effe/cting ignition ofy the initial gas and air mixture consequent upon the iirst opening of this door, whereby the subsequently formed mixture of said gas and air will burn without explosion as the said exit door is further opened.

5. A furnace having a chamber adapted to receive material for heat treatment, a door at the entrance of said chamber arranged to move vertically upward in opening and a gas conduit at the lower edge of said door with outlets disposed to project a gaseous curtain downward across the said entrance when the door is opened.

'6. A furnace having a chamber adapted to receive material for heat treatment; a door at the exit end of said chamber arranged to move vertically downward in opening; and means for moving said door comprising a link pivotally connected tovsaid door, a crank pivotably connected to said link, and a weight acting upon said crank tending to rotate it, and means causing said link and crank to assume an integral relation as they are moved to close said door, whereby the tendency of said crank to rotate is transmitted to said door so as to press it against its seat.

7 A furnacehaving a chamber adapted to receive material for heat treatment; a door at the eXit end of said chamber arranged to .move vertically across said exit in opening and in closing; and means for so moving said door comprising a weight and interconnected linkage whereby the force of said weight after acting to move Said door to closed posi,-

.door is further opened.

tion thereafter acts to press said door tightly being adapted upon the release of said holde ing means to cause said edge to remain tight and thev opposite edge of said door to open initially.

9. A furnace having a chamber adapted to receive material for heat treatment and having an opening; a door arranged to move vertically across said opening under the forcel of gravity; and cam means associated with the door and adapted to apply the force tendency to move said door across said opening as' a force holding said door tightly against the edgepf said opening.

10. A furnace havin-g a chamber adapted to receive material for heat treatment, a door at the entrance of said chamber arranged tomove vertically upward in open-` ing; a gas conduit at the lower edge of said door with outlets disposed project a gaseus curtain downward across the said entrance when the (door is opened; and means controlled in accordance with the movement of said door and governing the flow through said conduit..

.11. A special vatmosphere furnace having in combination, a chamber; means for the admission of special atmosphere gas to said chamber; an exit door at one end of said chamber arranged to open downward; and means providing a flame at the top edge of said exit door whereby upon the door being 4opened the initial mixture of the special atmosphere gas and air is ignited, and can thereafter burn without explosion as the said '12. Al furnace having, in combination, a

.heated chamber and a cooled chamber in can thereafter burn without explosion as the said door is further opened'.

13. A special atmosphere furnace havlng a chamber adapted to receive material for heat treatment; a conduit arranged to introduce a combustible gas withinsaid chamber; 4an vopening at one end of sald chamber; a.

door for closing said opening arranged move vertically downward thereacross 1n opening; and means providing a flame near the top edge of said opening whereby upon the door being opened the mixture of said combustible gas and air is ignited and can thereafter burn without explosion as the said door is further opened.

14. A furnace having a chamber adapted to receive material for heat treatment; a door at the entrance of said chamber arranged to move vertically downward across said entrance in opening; and a gas conduit extending across the entrance at its upper edge having outlets disposed to project a gaseous curtain downward across the said entrance when the door is opened.

l5. A furnace having a chamber adapted to receive material for heat treatment; a door at the entrance of said chamber arranged to move vertically downward across said entrance in opening; a gas conduit at the upper edge of said entrance having outlets disposed to project a gaseous curtain downward across said entrance when the door is opened; a

Valve controlling the fiowof gas in said conduit; and control means actuated by the movement of said door for opening and closing said valve.

16. A furnace having a chamber adapted to receive material for heat treatment; a door at the entrance of said chamber arranged to move vertically downward in opening; a gas conduit at the upper edge of said entrance having outlets disposed to project a gaseous curtain downward across said entrance when the door is opened; means over-balancing the weight of said door and adapted to held the door closed; means whereby the force of the last said lmeans may, be overcome and the door locked in open position.,

Signed at Attleboro, Massachusetts, this 17th day of April 1930.

JEWETT F. SCHRUMN; 

